this patch fixes compilation of gdbserver on systems that don't have
thread_db.h. in that case we fall back to gdb's own copy 
"gdb_thread_db.h", so the typedef of the td_thrhandle_t member is 
available, which is accessed in other parts of the code without
checking whether thread_db.h is available.
this is by far the cleaner solution, removing the accesses to the
th member in other parts of the source would either litter it with
ifdefs or cripple the functionality.

--- gdb-7.6.2.org/gdb/gdbserver/linux-low.h
+++ gdb-7.6.2/gdb/gdbserver/linux-low.h
@@ -18,6 +18,8 @@
 
 #ifdef HAVE_THREAD_DB_H
 #include <thread_db.h>
+#else
+#include "gdb_thread_db.h"
 #endif
 #include <signal.h>
 
@@ -270,11 +272,9 @@
   int need_step_over;
 
   int thread_known;
-#ifdef HAVE_THREAD_DB_H
   /* The thread handle, used for e.g. TLS access.  Only valid if
      THREAD_KNOWN is set.  */
   td_thrhandle_t th;
-#endif
 
   /* Arch-specific additions.  */
   struct arch_lwp_info *arch_private;
